The viscous resistance offered by a tube of varying radius to the flow of a liquid is discussed. Three cases are taken up, for which solutions assume the forms:(1) capillary tube viscometer:&eegr;=&pgr;P/8QAL.(2) Bingham and Murray plastometer:&eegr;=P(t−t1)/8[f3(l)−f3(l1)].(3) apparatus for studies of wetting under dynamic conditions:&ggr;=4&eegr;f5(l)/t.The functionsAL, f3(l), andf5(l), may be obtained from a calibration of the tube, use being made of graphical integration.